               (assert (= lower (aget keys 0)) (pr-str lower keys))
               (assert (= upper (aget keys (- (alength keys) 1)))))
             (do
-              (assert (= lower (.-lower (aget children 0))))
-              (assert (= upper (.-upper (aget children (- (alength children) 1)))))
+              (assert (= lower (.-lower (aget children 0))) (pr-str lower (.-lower (aget children 0))))
+              (assert (= upper (.-upper (aget children (- (alength children) 1)))) (pr-str upper (.-upper (aget children (- (alength children) 1)))))
               (assert (every? #(> (aget keys %) (.-upper (aget children %))) (range (count keys))))
               (assert (every? #(< (aget keys %) (.-lower (aget children (inc %)))) (range (count keys))))
               (dotimes [i (count children)] (.valid! (aget children i) min-keys max-keys))))))

                    (set! (.-parent child) right-node)
                    (set! (.-parent-ix child) ix)))
                (set! (.-children right-node) right-children)
                (.splice children median (+ median 2))))
            (.valid! this (js/Math.floor (/ max-keys 2)) max-keys)
            (.valid! right-node (js/Math.floor (/ max-keys 2)) max-keys)
            (.insert! parent parent-ix median-key median-val right-node max-keys)))
  (valid! [this min-keys max-keys]
          (assert (>= (count keys) min-keys) (pr-str keys min-keys))
          (assert (<= (count keys) max-keys) (pr-str keys max-keys))
          (assert (= (count keys)) (inc (count children)))
          (assert (= (count keys) (count (set keys))))

                (set! (.-lower right-node) (.-lower (aget children (+ median 1))))))
            (set! (.-keys right-node) (.slice keys (+ median 1)))
            (set! (.-vals right-node) (.slice vals (+ median 1)))
            (.splice keys median (alength keys))
            (.splice vals median (alength vals))
            (when-not (nil? children)
              (let [right-children (.slice children (+ median 1))]
                (dotimes [ix (alength right-children)]
